1. Field of the Invention
This invention relates generally to an improved roofing system. In particular, this invention relates to a well-insulated commercial greenhouse range roof glazing system without moving parts that externally maximizes the collection of fill spectrum winter sunlight while externally managing the summer sunlight input to similar levels while further factoring out potions of the light spectrum not vital for photosynthesis.
2. Description of Related Art
Primarily, greenhouses shield plants from the weather. Plants generally require five separate building related factors for growth. These factors are humidity, temperature, carbon dioxide, light and atmospheric pressure. Should variations in any one of these factors stray outside acceptable levels for a significant period of time, a plant may die.
Traditional greenhouse construction can only control some, but not all of these factors. When the present invention is incorporated in an appropriately designed greenhouse, all of these factors can be controlled.
Traditional greenhouses are typically located far from urban consumption centers, whereas the roofing system of the present invention enables greenhouses to be located closer to consumers, and, therefore, eliminates several links in the distribution chain, thus reducing labor, transportation, and spoilage costs. Further, the present invention enables several structures to be in close proximity to one another, something conventional greenhouse designs does not allow.
Several configurations of greenhouse and roof design are known. These disclosures suffer from numerous disadvantages, which are overcome by the present invention. For example, U.S. Pat. No. 5,261,184 to Appeldorn et al., discloses an internal optical system for a free standing greenhouse. Appeldorn et al. allows more light into the greenhouse in summer than in winter. This optical system is located inside of the structure and, therefore, does not control the amount of light energy that the plants require, or that the building has to deal with for heating and cooling. This is not the case with the present invention's design. Further, a greenhouse utilizing this type of optical system must be free standing and separated from other greenhouses, because structures were placed together, the ridgeline of one building would cause a shadow on the next building's glazed area. Utilizing Appeldorn et al.'s design requires the construction of more exterior walls, each wall having heat loss and gain, than the present invention.
U.S. Pat. No. 4,068,423 to Marsh, discloses simplified greenhouse assemblies designed to be field assembled from several subassemblies. In relation to solar radiation, the combined roof and sidewall structure is constructed of transparent corrugated fiberglass sheeting or panels with longitudinally aligned corrugations. Marsh discloses assemblies more typical of hobby house scale, unlike the commercial system of the present invention. Further, the walls and roof disclosed are of single glazing material which can not control heat loss and gain sufficiently to economically heat in winter and cool in summer. Another disadvantage is that the opening of the Marsh roof for ventilation does not allow for insect control.
U.S. Pat. No. 4,147,002 to Kautz, discloses a light valve system comprising spaced-apart sheets arranged to define a cavity therebetween. The sheets are formed from a light-transmitting material whereby light is transmitted through the cavity from one side to the other. Particulate material is conveyed in and out of the cavity to alter the light transmission through the cavity from one side to the other. The particulate material may be opaque or translucent depending on the degree of light restriction desired. The light valve system of Kautz is very dependent on electric controls, motors and mass movement of insulating particles. The time that it takes to fill and empty the cavities with this type of insulation appears to take longer than the time it would take for cloud cover to shade, and unshade, the greenhouse.
U.S. Pat. No. 4,209,222 to Posnansky, discloses an installation for utilizing solar energy, of the type having a plurality of reflectors capable of tracking the position of the sun for focusing the solar rays on at least one operative region.
U.S. Pat. No. 4,242,833 to Maes, Jr., discloses a method and apparatus for a greenhouse using a water layer disposed on the ceiling of the greenhouse such that the impinging solar radiation passes through the layer prior to passing into the interior of the enclosure. The water layer is contiguous to and partially defines the interior of the enclosure, such that the volume of water acts as a thermal storage medium. Relatively long wavelength infrared radiation is absorbed in the water while allowing passage of photosynthetic spectral regions of the solar radiation. Maes, Jr. also discloses assemblies of hobby house scale. If Maes, Jr. structures were connected together, the roofline of one building would shade the next building in the winter. Additionally, the water layer is horizontal and reflects the low winter sunlight off of the top surface of the ceiling to be reflected again by the underside of a movable reflector. The light would then exit the building through the curved glazing. This amounts to as much as 40% of the available sunlight. The winter light that strikes the underside of the movable reflector first will then be reflected back outside of the greenhouse after being reflected off of the surface of the water layer.
U.S. Pat. No. 4,586,297 to Tagiasco, discloses a greenhouse having a roof in the form of flat panels provided with regularly spaced undulations. The panels are made of a transparent plastic material, preferably polyester. The undulations are asymmetrical, and the panels are set up in such a way that that greater slope, i.e., the least inclined, is directed southward. Yet, this device does not control the amount of sunlight entering the structure. There would be over twice as much light in the summer as in the winter. Since the roof opens it can not protect the plants from insects, other plant pollen and weed seeds. Further, the thermal insulation characteristics are not adequate for economical heating and cooling.
U.S. Pat. No. 5,519,964 to Kujirai et al., discloses a composite plastic film and a greenhouse built with that film as a light-transmitting covering sheet material. The transparent or translucent plastic material film is a double-layered composite film consisting of a substrate film and a overlayer characterized in terms of the relative values of two parameters including the total heat volume and the absorbtivity of radiation heat. Although this single membrane may modify the radiant heat gain/loss characteristics, it does little to stop the heat gain/loss due to conduction. Control of this conduction is critical at night when outdoor temperatures are low.
U.S. Pat. No. 5,524,381 to Chahroudi, discloses a building having a series of multi-layered solar collectors comprising a layer of a transparent glazing material at the outer most surface of the multi-layer solar collector, a layer of a transparent insulation material, a layer of optical shutter and a heat storage element. Yet the top exterior surface of this glazing system is flat so that depending on the slope and orientation of the root, there will be sunlight striking this surface below the critical angle in the winter. This would account for up to 40% of the initial sunlight being reflected back up into the sky.
U.S. Pat. No. 5,585,418 to Nagata, discloses a thermoplastic greenhouse film having an outer layer with a variable light-diffuse surface wherein the film is clear to impinging sunlight on temperate days but which darkens on the effect of high, direct sunshine in order to prevent excess heat build-up within the greenhouse. The top surface of this system is also flat and therefore will also reflect up to 40% of the low angled sunlight back up to the sky. If buildings are connected together, and the gutters are running East/West, then the roof of one building would also shade the next building in the winter. Further, 100% of this type of roof has the heat loss of single or double glazing systems.
Unlike the operation of a conventional greenhouse, instead of using fuel such as electricity or fuel oil for constant operations, greenhouses comprising the present invention operate primarily on energy from sunlight. Compared to conventional greenhouses, the present system can result in savings of as much as 90% in fuel costs. In addition to the advantage of significant savings in fuel costs, the present roof glazing system also results in up to four times the productivity of conventional greenhouses. It is completely natural and relies on no chemicals whatsoever.
The present invention aids in providing growing climates for the production of produce and other plants. This system is better suited than the mainstream reliance on chemical pesticides, chemical herbicides, plant genetics, plant rotation and transportation.
Thus, it can be seen that there is a need for a well-insulated commercial greenhouse roof glazing system that integrally maximizes the collection of full spectrum winter sunlight while managing the summer sunlight input levels while further factoring out portions of the light spectrum not vital for photosynthesis, without the requirement that the present system be capable of movement, for example, solar tracking.